Grinding apparatus for disintegrating fibrous material



Feb. 14, 1961 s. H. JOHANSSON 2,971,704

GRINDING APPARATUS FOR DISINTEGRATING F IBROUS MATERIAL Filed NOV. 7, 1955. 2 Sheets-Sheet 1 Fig.1

/A l /vrae 51/6 HEEEEBT .7 01/4/7550 Feb. 14, 1961 Filed NOV. 7, 1955 S. H. JOHANSSON GRINDING APPARATUS FOR DISINTEG RATING FIBROUS MATERIAL 2 Sheets-Sheet 2 70 ss 110x 11.1. A

72 7a 63) 5:. as so 74 2 I N y NTO e Syf/y A EQGE IVJEI/A Nssua' GRINDING APPARATUS FOR DISINTEGRATING FIBROUS MATERIAL Sven Herbert Johansson, Bromma, Sweden,

Arne Johan Arthur Asplund, Bromma,

Filed Nov. 1, 1955, Ser. No. 545,497

1 Claim. (31. 241-37 assignor to Sweden This invention relates to grinding apparatus for the breaking down of fibrous material.

grinding member, such as in the form of grinding discs.

Examples for grinding apparatus of the type in consideration are finishing machines, pulp grinders and jordans.

In apparatus of said type at least one of the grinding members, preferably the rotatable member, is axially displaceable relatively to the other member to provide adjustment of the mutual spacing of the grinding members and of the compressive pressure exerted upon the fibrous material introduced into the spacing or grinding clearance between said members.

It is known in grinding apparatus of the type in consideration to eifect the axial displacement of the grinding member in the direction towards the other member by V means of a plunger rigidly secured to the displaceable grinding member and adapted to be displaced axially within a cylinder rigidly secured to the frame of the ap paratus by means of a pressure fluid acting on one face of said plunger. By said action of the pressure fluid the plunger is caused to move towards and finally to abut against a stationary stop or one which is rigidly attached to the frame of the apparatus. The pressure of the fluid is exerted only on one face of said plunger so as to cause it to exercise the compressive pressure required in the grinding operation.

The adjustment of the grinding members to the desired clearance between their working surfaces, which clearance in grinding apparatus for breaking down or disintegration of fibrous materials in aqueous suspension, such as paper pulp, is of the order of magnitude of one or a few hundredths millimeters while the grinding members have a diameter frequently amounting to 1.5 meters and more, is usually effected, unless the stop is adjustably secured to the frame of the apparatus, by means of a screw connection between said plunger and a holder member for the axially displaceable grinding member. By turning the plunger, the distance between the stop for said plunger and the axially displaceable grinding member is varied. During working operation of the apparatus a continuous readjustment of the grinding clearance is required as a consequence of the wear on the grinding members. If such readjustment shall be effected without interrupting the working operation a large force is necessary for turning the plunger pressed against the stop by the whole compressive pressure. In practice a transmission device is often provided in order toovercome the resistance to the turning movement of theplunger. Sometimes an axial thrust bearing assists further in facilitating said turning movement. Due to these additional members it has proved a diflicult and complicated operation'to adjust the axially displaceable grinding member relatively to the other grinding member so as to attain the desired exact spacing between them and in particular 5 2,971,704 Patented Feb. 14, 19 61 to maintain the exact grinding clearance required during the grinding operation to compensate for the continuous wear to which the opposed faces of the grinding members are subjected. As the machine parts abutting against the stationary stop are relatively heavy the contacting stopping surfaces must be relatively large and nevertheless exactly machined in order not to imperil the required exact size or true parallelism of the small grinding clearance.

One main object of the invention is to overcome the necessity of providing a mechanical stop for the plunger under its movement to force the axially displaceable grinding member towards the other grinding member when the predetermined spacing between said members is being reached.

A further object of the invention is to avoid the necessity of providing means to effect turning movement of said plunger.

A still further object of the invention is to provide simpler and nevertheless more effecting means than hithertofore bringing about a highly exact adjustment of the clearance between the grinding members.

A still further object of the invention is to provide improved means for continuous adjustment of said clearance during operation of the grinding apparatus in response to the continuous wear to which the opposed surfaces of the grinding members are subjected.

Further objects and advantages of the inventions will be apparent from the following description considered in connection with the accompanying drawings which form part of the specification and of which:

Fig. 1 is a more or less diagrammatic and partially sectional elevation of a grinding apparatus embodying the invention.

Fig. 2 is a more or less diagrammatic and partly sectional elevation of an impulse giving device forming part of the apparatus shown in Fig. 1 and represented in an enlarged scale compared with the scale of said Fig. 1.

Referring to the drawings, 10 designates a frame for a grinding apparatus, said frame carrying a shaft 12 rotatably mounted in two ball bearings 14 and 16, respectively. One end 18 of said shaft is attached to a driving electric motor not shown. The opposite end of the shaft 12 carries a socket 20 supporting a disc 22 carrying a grinding disc 24 which thus is rotated when the shaft 12 rotates. Said grinding disc is intended to co-operate with a stationary grinding disc 26 secured to a holder member 28 rigidly secured to the frame 10 of the apparatus. The grinding discs 24 and 26 may be of known construction with parallel channelled grinding surfaces. '30 designates the grinding clearance formed between the surfaces of the discs 24 and 26. Said grinding discs are enclosed in a casing 32, and the fibrous material to be treated is fed into the apparatus through a central opening in the holder member 28 by means of a conveyer screw 31.

The rotatable shaft 12 is with the clearance encased by a plunger 34 disposed axially displaceable within a sta tionary cylinder casing 36 rigidly connected with the frame 10. Said plunger 34 is disposed to slide with an annular flange 38 along the interior face of said cylinder casing 36. A cover 40 and an inwardly projecting flange 42 of the casing 36 limit the space available within said casing for the axial displacement of the plunger 34. In the embodiment shown, the surface 44 of the annular face 38 facing the cover 40 has a larger area than the surface 46 thereof facing the flange 42 of the cylinder. The end 48 of the plunger 34 directed towards the grinding disc 24 is rigidly secured to a bearing box 50 encasing the outer annular member of the ball bearing 16. The inner annular member of said ball bearing 16 is fixed between a nut 52 screwed on the shaft 12 and a' 3 shoulder 54 radially projecting from said shaft. The bearing box 50 is located within a bearing bushing 56 rigidly secured to the frame and rigidly connected to the front edge of the cylinder casing 36.

The space limited within the cylinder casing 36 by the wall 44 of the flange 38 and by the cover 40 and also the space limited therein by the wall 46 of said flange and the flange 42 are filled with a pressure fluid, preferably oil. The room 58 is connected through a conduit 64 and the room 60 through a conduit 62, to an impulse giving device generally designated by 66. Said device includes a preferably cylindrical plunger 68 adapted to be actuated in both faces by the pressure fluid and disposed axially displaceable within a correspondingly formed bore 70 extending inside the device 66 preferably parallel to the axis of the shaft 12. The plunger 68 has a smaller middle portion 76 disposed between two thicker end portions 72 and 74, respectively, the thickness of which is dimensioned so as to provide their sliding fit within the bore 70. Said middle portion 76 has a length slightly surpassing the distance between two radially extending recesses 78 and 80 of the bore 70 which latter is sealed against outward leakage by a cover 82 and a packing not shown adjacent the plunger portion 72. The conduit 62 from the space 60 opens into the recess 78 located adjacent the plunger portion 72, the conduit 64 from the the space 58 opening about half way between said recess 78 and the recess 80. From said last-named recess 80 a conduit 86 extends to an oil pan 88 from which the the pressure fluid, such as oil, is fed under the desired predetermined pressure by a continuously working pump 92 driven by an electric motor 90 through a conduit 94 into the conduit 62. and through a branch of said conduit directly into the space 60 and through another branch thereof into the recess 78 .and the conduit 64 into the bore 70. 84 denotes an, adjustable valve member locatedin a by-pass conduit 95 connecting the pressure conduit 94 directly with the oil pan 88. A support 96 secured to the plunger 34 carries a scaled adjusting screw, 98 intended to actuate the plunger 68 which when not actuated by said screw 98 is kept displaced to the left, viewed in the plane of Fig. l, by a spring 100 interposed be-. tween the free end face of the portion 74 of'the plunger 68 and the cover 82. Theplunger is displaceable against the action of said spring andadapted to be kept in said displaced position by means of a manually operated lever arm 102 pivotably mounted on the impulse. given device 66 and adapted to be locked, in. various. predetermined positions.

The apparatus constructed according, to the invention operates in the following manner. It is assumed that the grinding disc 24 of the apparatus is to be displaced by means of pressure oil supplied by. the continuously operating pump 92 so as to adjust the grinding clearance 30 to the position shown in Fig. l where the grinding clearance has the desired size, from an initial position in which said clearance is larger. In this initialposition of the disc 24 the plunger 34 keeps the support 96 spaced from the plunger 68 so much as to permit the spring 100 to force the plunger to the left, viewed inthe drawing plane past the balancing position shown in the Fig. 1. By said displacement of the plunger 68 the recess80 and therewith also the return conduit 86 leading to the oil pan 88 are sealed more or less completely. On the other hand, the recess 78 is laid open more than before. This causes the pressure oil, which is.fed-.into the apparatus by the pump 92 under constant pressure, to be conveyed through the conduit 62, the recess 78, past the central portion 78, past the centralportion 76 of the plunger 68 along the bore 7.0 into the conduit .64

and intospace 58, under substantially the same pressure under whichthe said pressure oil, is pumped throughthe conduit 94 and the other branch of the conduit .62 into the space 60. As the annular flange 38 has a larger area facing the space 58 thauthe areafacingthe room 60 the equal pressure now prevailing in both spaces will produce an excess of power within the space 58 forcing the plunger 34 to the right, viewed in the plane of the drawings. In this movement the adjusting screw 98 is carried along and displaces the plunger 68 to the right, viewed in the plane of the drawings, and causes a gradually increasing sealing of the recess 78 and a gradually increasing opening of the recess 80. As a result the pressure oil supplied by the pump 92. through the conduit 94 continuously maintains the same pressure within the space 60, but as the supply to the recess 70 is restricted while at the same time the return conduit 86 leading to the pan' 88 is opened to a larger extent, the pressure of the oil in the conduit 64 and therefore the pressure prevailing in the space 58 is quickly reduced. After some time the power developed within the space 60 under the constant pressure and acting on the minor area of the annular flange 38 will be capable of balancing the power developed within the space 58 which is gradually reduced in spite of the larger area of the annular flange 38 acted upon due to the gradual reduction of pressure. Said balancing of the forces acting simultaneously on either side of said annular flange 3-8 will end the displacement of the plunger 34 and keep said plunger in the position attained. By suitable adjusting of the scaled screw 98 this balancing condition can be attained for any desired position if the annular flange 38 and thereby the position of the plunger 34. As Zthe position of said plunger 34 directly governs the spacing of the axially displaceable grinding disc 24 relative the stationary grinding disc 26 it is readily understood that the spacing of the grinding disc 24 from the grinding disc 26 and as a consequence the size of the grinding clearance 30 is exactly adjustable by determining the balancing position of the plunger by means of adjusting the. scaled screw 98. The feature, that: the oil pressure simultaneously acts on both opposite faces of the annular. flange 38 of the plunger 34 permits the use of any mechanical stop for the parts of the apparatus carrying the axially displaceable grinding member when moving towards the stationary grinding member to be; dispensed with. The pressure from the suspension of fibrous material fed under pressure by the screw conveycr 31 through the central opening in the holder member 28 into the grinding clearance 30 between said grinding discs during the grinding operation may be neglected in this connection, as it is always counter-balanced by'a corresponding additional pressure of the pressure fluid acting within the space 58'on the face 44. The-holder 96 carrying the scaled screw 98 does not constituteany mechanical stopper for the movement of the parts of the apparatus carrying the displaceable grinding disc but only has to control the impulse giving device 66 which in turn sets free the considerable forces required to effect dis-placement, stoppage and locking ofthe axially dis.- placeable parts of the apparatus.

When it is desired immediately to separate the grinding discs from their operative position, the lever arm 102 is turned so as to displace the plunger 68 to the right against the action of the spring 100more than is indicated by the scaled screw 98. By this operation the gradual sealing of the recess 78 and the gradual opening of the recess 80 is increased over the efiect created by the screw 98. The supply of pressure fluid through the conduit 63 and the bore 70 to the conduit 64 and finally the space 58 is rapidly reduced while the pressure is kept constant within the space 60. The resulting diflerence in the pressure of. the fluidacting in opposite directions on the annular flange 38 initiates arapid displacement of the plunger 34 and together therewith therapiddisplacement il r ndin 1 .02 s d re n aw y am e.

disc 26 untilthe plunger 34 is stopped by titrev eoyer 40L Inlthis case the grinding apparatus is out; of ,operation for whichreason the disadvantages describedabove in qun q nwi h .a .ii t oppenfu parts. of. the. sphere tus carrying the axially displaceable grinding member when moving into and being maintained in the working position do not exist.

Upon return of the lever arm 102 into the position shown in Fig. 1 the spring 100 forces the plunger 68 towards the scaled screw 98, and the pressure fiuid system begins to operate again in the above described cycle, the position of the axially displaceable members relative to the parts rigidly secured to the frame of the apparatus being readjusted in response to the indications given by the scaled screw 98.

It frequently occurs that foreign particles, such as small scrap iron fragments, stones and the like, find their way into the apparatus and produce a rapid increase of pressure forcing the axial displaceable grinding disc 24 apart from the stationary grinding disc 26 and also displacing the plunger 34 so as to produce an instantaneous excess of pressure in the space 58. In order then immediately and automatically to bring the grinding disc out of operative position in order to prevent detrimental effects due to excessive strains, the apparatus is equipped with a safety device. Said device is suitably connected to the impulse giving device and may have the construction illustrated in Fig. 2. The safety device includes a housing 104 mounted on the impulse giving device 66 and encasing a shutter 106 disposed slidable within said housing. Adjacent one front surface of said shutter the housing is connected to the bore 70 by a conduit 108 in a manner diagrammatically indicated in Fig. 2 by dashed lines. The opposite end 110 of the shutter 106 is formed with a wedge-shaped taper penetrating through an elongated slot 112 provided in the plunger portion 72. Said slot is dimensioned so as to allow axial displacement of the plunger within the bore 70 as a result of the action of either the spring 100 or the adjusting screw 98 and the lever arm 102, respectively. The lateral surface 144 of the slot facing said wedgeshaped taper 110 is at least partly formed so as to correspond to said wedge. The shutter 106 is kept in inactive position by a spring-actuated ball 116 positioned within an annular recess 118 formed in the lateral wall of said shutter. When the high excess pressure produced in the space 58 is transferred through the conduit 64 to the bore 70 and therefrom by the conduit 108 to the adjacent end face of the shutter 106, said shutter is forced deeper into the slot 112 provided that the pressure transferred through the conduit 108 is sufiiciently high to force the shutter to displace the ball 116 against the action of the spring forcing said ball into the recess 108. The wedgeshaped surfaces sliding against one another cause a rapid displacement of the plunger 72 so as immediately and completely to open the recess 80 and therewith the connection 86 to the oil pan 88 and at the same time immediately to close the recess 78 and thus to interrupt the supply of pressure oil through the conduit 64 to the space 58. This operation will result in an almost instantaneous reduction of the excess pressure prevailing in the space 58 rapidly followed by a further reduction of the pressure in said room causing the rapid removal of the grinding disc 24 out of its operative position almost adjacent the grinding disc 26.

In some cases it is advantageous to construct the annular flange 38 of the plunger 34 with its faces 44 and 46 of equal area to be actuated in opposite directions by the pressure fluid and to cause any desired displacement of said plunger by means of creating a difference in the pressure prevailing in the spaces 58 and 60, respectively, the balancing position of the plunger being attained by producing equal pressure in said spaces.

The impulse giving device 66 may be constructed so that on displacement of the plunger 68 within the bore 70 by the scaled screw 98 or the lever arm 102, respectively, it will more or less completely open the direct connection from said bore 70 to the oil pan without simultaneously reducing the supply of pressure fluid to one or the other of the spaces 58 or 60, respectively. The impulse giving device may aiso be disposed displaceable relatively to the plunger 34, its adjusting then not being effected by an adjusting screw supported by a holder rigidly secured to said plunger but by adjusting the location of the impulse giving device relative to said plunger. The release of the shutter 106 to cause displacement of the plunger 68 of the impulse giving device may be initiated by an electric impulse resulting from an overload of the driving electric motor caused by an increase of the resistance to rotation of the rotating grinding disc produced by the foreign particle present in the grinding clearance between said rotating grinding disc and the stationary grinding disc.

While one more or less specific embodiment of the invention has been described it is to be understood that this is for purpose of illustration only and that the invention is not to be limited thereby, but its scope is to be determined by the amended claim.

What I claim is:

A grinding apparatus for fibrous material comprising, a rotatable grinding element, a stationary grinding element, one of said elements being axially movable with respect to the other for the purpose of adjusting the width of the grinding space between the said grinding elements and for the purpose of conveying the grinding pressure, said axially movable grinding element being fixedly connected to a piston arranged for movement in a fixedly mounted cylinder, said cylinder having chambers on each side of the piston conneetible by means of a conduit and a valve to a pressure source and a discharge, the valve having a body axially adjustable with respect to the piston for the purpose of adjusting the piston to a predetermined Width of the grinding space between the grinding elements, said valve body being so coupled to the piston that any deviation from this width due to variations in the rate of feed will cause the valve body to accompany the piston in its axial movements and thereby while both chambers are connected to the pressure source produce a variable pressure differential on the piston so that the axial forces affecting the piston will always operate to return the piston to a position to restore the predetermined width of the grinding space.

References Cited in the file of this patent UNITED STATES PATENTS 614,316 Baker et al Nov. 15, 1898 901,770 Anthony Oct. 20, 1908 1,984,869 Parley et al Dec. 18, 1934 2,008,892 Aspluud July 23, 1935 2,156,320 Sutherland May 2, 1939 2,309,376 Avery Jan. 26, 1943 2,599,543 Coghill et al June 10, 1952 2,646,728 Coghill et al July 28, 1953 2,674,928 Coghill Apr. 13, 1954 FOREIGN PATENTS 13,428 Austria Sept. 25, 1903 111,803 Australia Oct. 24, 1940 175,765 Austria Jan. 15, 1953 512,978 Belgium July 19, 1952 

